The Application of Digital Infrared Thermal Imaging in Peripheral Artery Disease of the Lower Extremities

Peripheral artery disease (PAD) is highly prevalent. It occurs most often in the lower extremities. Symptoms include intermittent claudication, ischemic pain, ulceration and necrosis. Amputation may be necessary in severe cases. PAD is also an indicator of future cerebrovascular and cardiovascular events. Diabetes mellitus (DM) is one of the major risk factors of PAD. Approximately 5% to 10% of diabetic patients have had foot ulceration, and 1% have undergone amputation. Other risk factors include smoking, old age, male gender, hypertension, dyslipidemia, hyperhomocysteinemia and renal insufficiency. Ankle-brachial index (ABI) is the most popular tool used to screen PAD. Doppler-derived ankle and brachial systolic pressure is obtained. If the ratio is abnormal, further confirmation studies will necessary. Although ABI is recommended as one of the screening tests for diabetic complications in guidelines, its utility is limited in calcified non-compressible vessels, which are common in DM and renal failure patients. Digital infrared thermal imaging (DITI) is used to detect surface temperature because objects of absolute temperatures higher than zero would radiate electromagnetic waves of certain wave lengths according to Plank's law. DITI examination is non-invasive, non-contact and fast. Theoretically, temperature of the perfusion area of the occlusive arteries will decrease. Investigators will analyze DITI of PAD, and observe the relationship between DITI, ABI and vascular duplex examination. The dynamic change of DITI before and after percutaneous transluminal angioplasty of PAD will also be observed. Investigators would like to evaluate the possibility of the clinical application of DITI for PAD screening.